Load interrupter switch



June 10, 1958 K. H. DATE LOAD INTERRUPTER SWITCH 3 Sheets-Sheet 1 FiledMay 28, 195

INVEN TOR. ifizuo Henry Date Md W flbt'arnqy' June 10, 1958 K. H. DATELOAD INTERRUPTER SWITCH 3 Sheets-Sheet 2 Filed May 28, 1956 IN V EN TOR.k'azua fie/27y Date June 10, 1958 K. H. DATE 2,333,638

LOAD INTERRUPTER SWITCH Filed May 28, 1956 5 Sheets-Sheet 3 IIHIIHI INVEN TOR. Kazua Henry .Date

flttorney United States Patent LGAD INTERRUPTER SWITCH Kazuo Henry Date,South Milwaukee, Wis., assignor to McGraw-Edison Company, a corporationof Delaware Application May 28, 1956, Serial No. 587,873

2 Claims. ((31. 200-146) This invention relates to a high voltage airdisconnect switch in combination with an auxiliary path load currentinterrupter.

It is common practice to use air disconnect switches for sectionalizingpower distribution systems but it is usually necessary to back them upwith a circuit breaker capable of interrupting load current so that thesectionalizing switches may be opened while not conducting electricity.If the air disconnect switches are opened without previouslyde-energizing the circuit, a destructive arc may be drawn between theswitch blade and its cooperating jaw contact. Because under modern conditions very important electric loads may be connected to the system, itis seldom practical to de-energize the whole circuit when it is desiredto sectionalize a portion thereof and for this reason it has becomedesirable to adapt air disconnect switches for interrupting their ratedload current. it is becoming more common to do this by attaching anauxiliary device which confines the arc, incident to opening the switch,to an enclosed arcing chamber which takes on the status of a preferredcurrent path while the switch is being opened.

Although such load interrupters are obviously desirable, their use hasnot become as extensive as might be expected because of the diiiicultyof adapting them to pro-existing switches and because they haveheretofore been comparatively expensive.

Accordingly, it is a general object of this invention to provide aneconomical, compact, easily installed and effective load interrupter forcoaction with an air disconnect switch.

A further object is to provide a load interrupter that is versatile inthe respect that it is adaptable to currently manufactured switches orto a variety of switches already installed in power distributionsystems.

. A further object is the provision of a switch and auxiliary loadinterrupter combination which acts positively, that is, which asstuesthat the auxiliary load interrupter will close and open only inaccordance with a desired corresponding full opening and closing of thecooperating disconnect switch.

Another important object is to provide an assembly of the aboveindicated type which obviates drawing of damaging arcs between parts ofthe disconnect switch while interrupting its rated current.

Yet another object is to provide an auxiliary interrupter and disconnectswitch combination which is unaffected by weather, requires a minimum ofattention and operates reliably and positively under adverse conditionssuch as when heavily coated with ice.

Attainment of the atoregoing and other objects will become apparentthroughout the course of the ensuing specification.

In general terms, a preferred form of the instant invention ischaracterized by its including an air-disconnect switch having a bladewhich rotates on its longitudinal axis while swinging on its transverseaxis to an open position. The movable blades engagement with 2,838,638Patented June 10, 1958 a stationary contact jaw constitutes a maincurrent carrying path of the air disconnect switch.

In parallel with the air gap created by separation of the movable bladesfrom the stationary contact jaw, is an auxiliary path includinginterrupting contacts in series with a bypass rod which maintainscircuit continuity while the main blade is being operated toward openposition and assures a by-pass circuit before the main blade is closed.Suitable quick acting mechanism is also provided for actuating theinterrupting contacts when the main blade has swung to a predeterminedposition where the latter acts on the interrupter trip arm and thusopens the circuit through the by-pass rod. Further swinging movement ofthe main switch blade causes it to carry the by-pass rod into isolatingspaced relation from the interrupter, allowing visual determination ofwhether the switch is in full open position.

A more detailed explanation of the invention will be set forth inconnection with the drawing in which:

Fig. 1 is a side elevation, partly in section, of the air disconnectswitch and auxiliary load interrupter combination, both the switch andinterrupter being shown in closed circuit position;

Fig. 2 is a view similar to Fig. 1, but showing the switch andinterrupter in open circuit position;

Fig. 3 is a fragmentary sectional view, showing parts of theinterrupter, taken on a line corresponding with 3--3 in Fig. 1; and,

Fig. 4 is a left side elevational view, partly in section, taken on aline 4-4 of Fig. 1 and with parts broken away.

A typical three insulator, rotating and twisting blade, vertical break,air disconnect switch, designated generally by the reference numeral 1,is shown in Fig. 1 in combination with an auxiliary interruptergenerally designated 2.

Switch 1 comprises a stationary contact jaw 3 mounted on a cast metalterminal adapter 4 supported on a stationary insulator 5. When switch 1is closed as in Fig. 1, jaw 3 receives a movable, swinging and axiallytwisting blade 6 in high pressure electrical engagement. Blade 6 isadapted to swing into open position on a transverse axis coincident withthat of a pair of hexagon headed trunnion pins 7 While it twists in ablade guide 8 about its longitudinal axis. This action is brought aboutby axial rotation of a center insulator 9 which carries a crank arm 10terminating in a universal connection 11. Force from crank 10 istransmitted to blade 6 through a link 12 clamped to the blade by a bladecarriage 13 having an extension journalled in blade guide 8. It isevident that blade 6 Will be disconnected from jaw contact 3 in Fig. 1while being twisted and swung to its position in Fig. 2, when insulator9 is rotated axially.

Trunnions 7 are partially threaded and screw into the spaced yoke arms14 of a fixed metallic frame 15 which is journalled with respect toinsulator 9 but anchored on a third insulator 20. A power line may beconnected to the frame 15 on a casting extension 21. Frame 15 alsosupports a fixed contact jaw 22 which is in line with blade 6 andelectrically engages the hinge end of the blade when the switch isclosed as in Fig. l, wh reas the blade swings free from jaw 22 when theswitch is open as in Fig. 2.

The auxiliary path load interrupter 2 which cooperates with airdisconnect switch 1 is mounted on a conductive base casting 24 bolted at25 to contact jaw terminal adapter 4. Base 24 has a portion 26 forconnecting an incoming line wire, not shown. it is evident from thedescription thus far that the normal, main current path to disconnectswitch 1 commences at incoming adapter portion 26, extends through blade6 to contact jaw 22 and terminates in outgoing adapter 21 forming partof frame 15.

A more detailed description of the air disconnect switch 1 is set forthin the copending application of T. A. Fjellstedt, S. N. 449,129, filedAugust 11, 1954 and assigned to the instant assignee.

Having described the principal current path through the air disconnectswitch 1, attention is now invited to he auxiliary path load interrupter2 and by-pass rod 28 which together constitute a parallel preferentialpath when the main switch 1 is being opened under load.

Load interrupter 2 includes a hollow porcelain bushing 29 which isfilled with oil to'the dashed line 3%} and houses an arcing chamber 31.A removable fluid measuring rod 19 projects beneath the fiuid todetermine its depth. An oil filled interrupter is preferable for theduty here involved because it inherently maintains its dielectricstrength so that an arc is not prematurely struck when the movablecontact approaches the stationary contact during closing of theinterrupter. An air or gas filled interrupter is more inclined towardprestriking an are before the contacts are fully closed and thereforenecessitates higher contact speeds in order to minimize arc duration andenergy and to overcome the tendency for the contacts to blow open due tothe pressure of hot gases incident to arcing. The are extinguishingstructure housed by porcelain bushing 29 is described in detail in acopending application of A. Van Ryan, S. N. 563,014 filed February 2,1956, and assigned to the instant assignee. For understanding thepresent invention, however, it is suflicie nt to realize that the arcextinguishing chamber 31 includes near its bottom a fixed contact, notshown, but in electrical connection with conductive base 24 and whichcooperates with a movable contact rod 32 to open and close a circuitthrough interrupter 2. Movable contact rod 32 is adapted to execute astraight line movement centrally of bushing 29 and to project into ametal housing 33 which encloses contact moving mechanism designatedgenerally by the reference numeral 34. Current is interchanged directlyfrom movable rod 32 to housing 33 by conventional wiping contactfingers, not shown, attached to the bottom of the housing 33 within theupper end of arcing chamber 31.

Movable contact 32 is indirectly actuated by main blade 6 oscillating anexternal trip arm 35 journalled in spaced sleeve bearings 36 which fittightly into the sides of metal housing 33. Trip arm 35 is actually adouble arm member supported on each side on short coaxial transverseshafts 37 disposed through sleeve bearings 36, see Fig. 3. Arm 35 isattached to shafts 37 through the agency of caps 38 by staking or othermeans, the caps being pinned to the shafts. Shafts 37 are sealed bytightly interposing an O-ring 27 between arm 35 and a radial flange onsleeve bearing 36.

The sides of trip arm 35 are bridged exteriorly of the interrupterhousing 33 by means of a pair'of cross rods 39 and 40 spacedcircumferentially from each other. It will be noted that when main blade6 swings about its transverse axis '7 that a blade extension 45, carriedby blade 6, projects positively into driving engagement with the triparm between the two cross rods 39 and 40. This is also true when mainblade 6 is swinging from its open position in Fig. 2 toward closedposition. Blade extension 45 always engages trip arm 35 between crossrods 39, 40 so that if main blade 6 is opened sufiiciently to strikecross rod 39 and then reversed and brought back into closed switchposition, trip arm 35 will always follow the blade 6, thereby assuringthat the interrupter 2 circuit is closed when the switch 1 is closed andthat the interrupter opens only when the main switch opens.

The mechanism 34 located'within housing 33for opening the circuit tointerrupter 2 by accelerating movable contact 32 axially, is a quickacting, spring loaded toggle arrangement which does not begin to movecontact rod 32 until a. predetermined toggle position is reached,

whereupon all of the spring energy is suddenly applied to opening theinterrupter. The toggle mechanism is, of course, actuated in accordancewith positions of trip arm 35. Referring particularly to Figs. 1 and 3,the toggle linkage comprises a pair of parallel spring loading levers 46secured to shaft 57 by staking at ii or by other suitable means. A crosspin 48 joins levers 46 and is surrounded by a loose sleeve 49 to whichan end of each toggle spring 559 is attached. Swinging of lovers 4-6 bychanging the angular position of trip arm 35 tends to stretch and loadspring 53, as will be more apparent hereinafter.

Movable interrupting contact rod 32 is carried by a pair of parallellinks 51 which are pivotally connected to parallel levers 52 ata pivotjoint 53. The other end of levers 52 is pivoted for swinging about afixed pin 54 spanning spaced upright flat posts Springs 5t? arestretched between pivot 53 and cross sleeve 48 so that when theinterrupter is either closed as in Fig. l or open as in Fig. 2 there istension in the spring which holds rod 32 in a positive up or downposition, respectively. It will be observed that the line of action ofsprings 50 is below fixed pivot 54 when the movable contact 32 is downas in Fig. l and the line of action is above pivot 54 in Fig. 2 wherethe interrupter 2 is shown in opened position. Accordingly, when triparm 35 is swung to an intermediate position, causing the line of actionof springs 50 to coincide with a straight line between pivot 53 and 54,the mechanism is in toggle position whereupon further movement in onedirection or another will cause contact rod 32 to be projected axiallywith a snap action.

One end of contact carrying link 53 is pivoted to a compensating link 56pivoting on an anchor post 57 attached to the bottom of housing 33 byscrew means. Link 56 executes an oscillatory movement which compensatesfor the circular displacement of the other pivots during operation ofthe mechanism and allows contact rod 32 to follow an unrestrainedstraight line movement.

Link 51 pivotally attaches to a trunnioned thimble 58 connected withcontact rod 32. When contact rod 32 reaches its lowermost position,thimble 58 strikes a shock absorbing ring made up in laminar form ofmetal and rubber washers. Upward movement of rod 32 is arrested whenthimble 58 strikes a similarly constructed shock absorber 6t? screwedonto the top of housing 33 as shown.

In order to avoid arcing when blade 6 is separated from its cooperatingcontact jaw 3 under load, a parallel path must be maintained through theinterrupter to the hinge end of main switch 1. This is achieved by meansof a by-pass rod 23 which forms a bridge between a V-slotted rod stopcontact 65, secured to the top of metallic housing 33 and a hinge end ofblade 6. It is preferable to make by-pass rod 23 of highly conductivematerial such as Phosphor bronze having some rigidity but enoughresilience to augment electrical contact pressure with the rod stop whenblade 6 is in closed position. Note that by-pass rod 28 bows slightlywhen the main switch 1 is closed as in Fig. l in order to enhancepressure on rod stop 65.

By-pass rod 28 is supported for rotation on trunnion 7 at the hinge endof the main switch 1 on spaced members as in the nature of a pair ofbell cranks. The bell crank members 66 are spanned by tubular stringers67 and 63 which are each drilled radially for passing by-pass rod 28therethrough. Tubular stringers 67, 68 are also drilled at right anglesto the rod 28 for receiving rod clamping set screws 69 and 70. Set screw70 may be a socket head type. It is preferable, however, that set screw69 extend beyond the margin of bell crank arm 66 and to provide theformer with a jam nut 71 for fixing the adjustment of the screw withrespect to blade guide 8- which strikes screw 63 when the 'by-pass rod28 is carried back as in Fig. 2. V

Trunnions 7 are each surrounded, on an unthreaded portion, by a torsionspring 72 having one end bearing exerting a normally counterclockwiseforce on the-hook shaped short pressure arm 66' of bell crank member 66.It is evident that torsion spring 72 will supplement contact pressurebetween by-pass rod 28 and its cooperating rod stop contact 65 on theinterrupter housing 33. The primary contact pressure for by-pass rod 28,however, is derived from a force transmitted to the short end 66 of bellcrank member 66 by means of a stud pin 74 anchored in blade guide 8 andextending radially therefrom. The configuration of one stud pin 74 isclearly evident in Fig. 4 where its companion on the right hand side ofthat view is broken away. When main switch 1 is in closed position, anappreciable force from the switch closing mechanism is transmitted tothe relatively stiff by-pass rod by means of stud 74 so that the rod 28will make positive connection with rod stops 65 despite the presence ofice or any other contaminants which tend to increase contact resistance.

It is evident that when opening movement of main blade 6 is initiated,torsion spring 72 will maintain bypass rod 28 in good contact relationwith rod stop contact 65 even though stud 74 will at that time begin todepart from the short end 66' of bell crank lever 66. When main blade 6has swung through a predetermined angle, blade guide 8 strikesadjustable screw 69 and thereby positively carries by-pass rod 28through a visibly open position as in Fig. 2.

Observe in Fig. 2 that stud pin 74 is free of short end 66' of the bellcrank member 66 when the switch is fully opened. When closing switch 1,however, the angular spacing of the elements just mentioned is such thatstud 74 will begin to increase the bearing pressure on by-pass rod 28after it has been arrested by stop contact 65 on the interrupter butbefore trip arm 35 has been moved sufiiciently by blade extension 45 toclose the interrupter. Hence, rod 28 makes high pressure engagement withstop contact 65 before the rod begins conducting during closing ofswitch 1.

An electric circuit may be interrupted under full load conditions by anovel structure just described in the following manner: Insulator 9 isrotated to initiate twisting and angular swinging movement of mainswitch blade 6, causing free end of blade 6 to separate from stationarycontact jaw 3 and create an air gap therebetween, whereupon the mainload current passes through the auxiliary load interrupter 2 andcontinues to the hinge end of main switch 1 through the agency ofby-pass rod 28. As swinging movement of blade 6 is continued, bladeextension rod 45 passes between cross rods 39 and 40 and strikes 39carried by the interrupter trip arm. Continued swinging movement ofblade 6 causes trip arm 35 to rotate in a counterclockwise directionwhile simultaneously stretching toggle spring 51) interiorly of housing33. During this interval by-pass rod 28 remains stationary and inconductive relation with rod contact 65. As rotation of main blade 6continues, spring 50 reaches its over-center position whereupon itexerts its full vertical component of force upon movable interruptingcontact rod 32, thereby opening the latter with a snap action. Allarcing takes place within the arcing chamber 31 because during this timecircuit continuity in parallel with the gap created by opening switchblade 6 is maintained by by-pass rod 28.

After interrupter 2 has tripped, blade guide 8 continues its radialswing along with blade 6 until the guide strikes adjustable screw 69driving the by-pass rod out of contact engagement with stop 65 andcompletely opening the circuit through the interrupter. This actionproceeds until blade 6 has swung to more than 100, whereupon the maximumair gap is established between the interrupter, and blade 6 and by-passrod 28.

Reclosing of main switch 1 is again accomplished by rotation ofinsulator 9 in an opposite direction about its axis. This causes bladeextension 45 to precede by-pass rod 28 in a counterclockwise directionuntil extension 45 strikes the lowermost cross rod 40 of trip arm 35 asshown Fig. 2. Continued closing of the main switch rotates trip arm 35in a clockwise direction and by-pass rod 28 comes down and makes contactwith rod stop 65 before auxiliary interrupter 2 closes its circuit. Triparm 35 closes interrupter 2 prior to the engagement of main blade 6 withits cooperating stationary contact jaw 3 so that the current takes theauxiliary path to load interrupter 2 before circuit continuity isestablished through main switch 1.

It is an important feature of the present invention that main switchblade 6 cannot be swung to a partially open position where itinadvertently trips the circuit interrupter open and then be restored toengagement with stationary contact jaw 3 while the interrupter 2 isopen. This is so because blade extension rod 45 only engages trip arm 35between one or the other of cross rods 39 and 40, so that onceengagement with either of the cross rods is effected, trip arm 35 mustpositively follow the direction established by rotation of main blade 6.Accordingly, if main blade 6 is partially opened it can only be reclosedsubsequent to reclosure of the parallel path through auxiliary loadinterrupter 2 and it is impossible to draw an are between blade 6 andstationary jaw 3 whether the switch is being opened or closed.

Although a preferred arrangement of the load interrupter has beendescribed in conjunction with a particular form of air disconnectswitch, it is to be appreciated that the interrupter may takealternative forms and that it is readily adaptable to a variety of priorart air disconnect switches of the rotating and twisting blade types. Itis further apparent that the supporting base casting 24, for tubularporcelain bushing 29, may be easily bolted to any form of terminaladapter such as 4 here serving as an illustrative example. Likewise, thebell crank supporting member 66 for by-pass rod 28 may be convenientlyadapted to any switch having a transverse axis of rotation for its mainblade and by-pass rod 28 may also be mounted directly on a blade such as6.

The hereinabove described preferred embodiment of the invention is notto be construed as limiting the invention for it may be variouslyembodied and is to be interpreted as claimed.

It is claimed:

1. The combination of an air disconnect switch and a load interrupter,said switch including a stationary jaw means and a cooperable switchblade, blade guide means in which said blade is journalled for rotationon its longitudinal axis, said guide means being pivoted on an axistransverse to the blade axis for swinging the blade through angularpositions into and out of engagement with the jaw means, a loadinterrupter having its lower end in conductive relation with the jawmeans and extending generally along the swinging path of the blade, atrip arm operatively and pivotally connected to said load interrupternear its upper end, said trip arm extending into the blade path forbeing engaged by the blade when the latter is in intermediate angularpositions, a by-pass rod means releasably engageable with a portion ofsaid interrupter more remote from the jaw than said trip arm, crankmeans pivotally supporting said by-pass rod means for swinging in thedirection of the blade means about said transverse axis, said crankmeans including an extension arm means, driving pin means carried by theblade guide means in the path of said extension arm means and angularlyspaced therefrom when said switch blade is angularly remote from saidjaw, said driving pin means engaging said extension arm means forpositively increasing pressure on said by-pass rod means when said blademeans is between its intermediate angular position and engagement withsaid jaw.

2. The combination of an air disconnect switch and a load interrupter,said switch comprising a pair of spaced terminals, a jaw on oneterminal, a blade hingedly mounted on an axis on the other terminaltransverse to its own longitudinal axis for swinging the blade throughangular positions into and out of engagement with said jaw, a loadinterrupter disposed outside the swinging path of said' blade, saidinterrupter having spaced terminals one of which is connected to saidjaw and the other of which is remote from said jaw, a movable contactadapted to bridge said interrupter terminals, means for operating saidmovable contact including a trip arm extending pivvotally from saidupper interrupter terminal into the path of said blade, a bypass rodmeans pivotally mounted on said other switch terminal, said rod meansbeing biased for swinging with said blade toward engagement with saidother interrupter terminal when said blade is in angular positionsbetween engagement with said trip arm and said jaw, crank meanspivotally supporting said by-pass rod, and driving means swingable withthe blade" but in lost motion relation with the crank means when:

References Qited in the file of this patent UNITED STATES PATENTS HoweJan. 7, 1941 Lingal Oct. 30, 1956

